Robert Haas <robertmhaas@gmail.com> writes:
> I don't believe you are fairly stating the consensus from previous
> discussion and I believe that you are actually in the minority on this
> one. I agree that we probably don't need to support this for object
> types for which CREATE OR REPLACE is available or can be made
> available, but that isn't feasible for all object types - tables and
> columns being the obvious examples.
What's obvious about it? In particular, I should think that ADD OR
REPLACE COLUMN would usefully be defined as "ADD if no such column,
else ALTER COLUMN as necessary to match this spec". Dropping the
ALTER part of that has no benefit except to lazy implementors; it
certainly is not more useful to users if they can't be sure of the
column properties after issuing the command.
regards, tom lane